Treatment of hydrocarbons



TREATMENT oF HYDRoCARBoNs Fild DeC. 3, 1931 ww Y Hh T1 i Patented Mar. 5, 1935 UNITED STATES PATENT OFFICE TREATMENT F HYDROCARBONS Jacque C. Morrell, Chicago, Ill., assigner to Universal Oil Products Company, Chicago, Ill., a corporation of South Dakota Application December 3, 1931, Serial No. 578,752

2 Claims. (Cl. 196-63) This invention relates to the treatment of tar acids and refers more particularly to the treatment of tar acids obtained from the distillates produced from coals at low temperatures.

5 More specifically the invention is concerned with a process for the manufacture of low boiling aromatic hydrocarbons and low boiling phenolic derivatives by a special method of treatment at elevated temperatures and pressures,

the details of operation ofthe process being fully disclosed in the following specification so as to make its novelty and utility evident to those skilled in the arts to which itr pertains.

The tars produced in distilling bituminous coals at temperatures commonly included within the range of 900 to 1100o F. are referred to in the trade as low temperature tars and the processes involved in their manufacture are similarly referred to as those of low temperature carboni- 2o zation. Solid fuels of high heating value and of relatively low smoking tendency remain as residues in the distillation retorts. Tar distillates thus produced, in contradistinction to the high temperature carbonization processes in which the production of liquid by-products is minimized, contain relatively small percentages of such aromatic hydrocarbons as benzene, toluene, naphthalene, anthracene, etc., characteristic of high temperature tars,\but contain proportionately larger amounts of high boiling hydrocarbons similar to those obtained from petroleum and also high boiling tar acids or phenols with which the process of the present invention is concerned. 'I'hese latter compounds may constitute as much as 50% of the total low temperature distillate, and are readily separable therefrom by a treatment with caustic soda solutions which form water soluble phenolates, the original phenols reappearing as a distinct 40 layer upon acidification of the alkaline solution. While the exact chemical composition of any particular low temperature coal tar is a matter -to be determined by analysis, sufficient work has been done on representative samples to indicate their average approximate composition.- They contain vminor amounts of phenol, large percentages of cresols (30 to 40%), numerous xylenols, higher phenol homologues in the amount approximately equivalent to the cresols and a limited amount of pitch which consists of acid resins to which the name of rhetinols has been applied. In the cresols th'e para compounds usually occur in predominating amounts. As to the exact nature of the high boiling homologues it may be said that they containy many naphltions may be conducted.

thol derivatives, that unsaturated and polyhydric phenols are present and that highly methylated phenols occur such as trimethyl phenol.

The series vof compounds containing phenol and its derivatives constituting the alkali-solu- 5 ble portion of low temperature coal tar behaves to some extent similarly to'corresponding boiling point hydrocarbon distillates when subjected to elevated temperatures and pressures, there being a general rearrangement of the molecular 10 structure with the production on the one hand of xed gases, lower boiling phenols and heavy residues, but in addition to these reactions a definite amount of reduction of the substituent groups in the aromatic rings occurs so that to a 15 certain extent the hydroxyl groups are reduced to produce water and a corresponding aromatic compound and the methyl and other similar substituent groups are reduced to form low boiling paraiiin hydrocarbons, the net results being 20 an unexpectedly high percentage of low boiling aromatic compound. The coke and gas forming tendencies of the tar acids are also high and caremust usually be exercised to keep the temperature below a certain maximum, to avoid 25 difiicultie's from coke deposition.

The present invention in one specic embodiment comprises the following general operations: heating tar acids at elevated temperatures and pressures in the presence of steam, separating 30 vaporous from nonvaporous reaction products, fractionating the vaporous products to produce a distillate of controlled, boiling point range and insufficiently converted liquid reuxes, returning the intermediate insufficiently converted re- 35 fluxes to the heating zone for further conversion, passing the vapors mixed with reducing gases over catalytic material, fractionating the reduced products to produceoverhead vapors of controlled boiling point range which are cooled, condensed 40 and collected and further intermediate insufficiently converted reiluxes which are returned to the heating zone for further conversion.v

A characteristic operation of the process may be conveniently described and the vnature of the 45 invention made clear by reference to the accompanying drawingwhich shows diagrammatically -by the useA of conventional gures in side elevation a combination of elements in which opera- 50 Referring to the drawing, tar acids may be fed to a pump 3 through a line `1 containing control valve 2 and vdischarged by way of a line 4 and the valve 5 through a heating element 6 disposed to. receive heat from a furnace 7. vThe heating 55 element and furnace may be of any suitable type, the former for example, being similar to the continuous end connected coils common to commercial cracking processes and the latter designed to heat the coil by convectional or radiant heat or both.

Controlled amounts of steam may be introduced into line 4 from a line 1 containing a valve 2' at a point preceding the heating element and during the passage of the tar acids and steami ment. At this point a particular feature of the invention may be brought out, that is, that within certain limits the addition of increased amounts of steam to the tar acids in the heating zone increases the ratio of hydrocarbons to phenols in the reaction products, this fact having been ascertained by repeated trials. For example, in cracking a particular tar acid at 175 lbs. pressure and a temperature at the exit of the heating element of approximately 885 F. the percentage of neutral hydrocarbon oil in the pressure distillate produced was increased from by raising the amount of steam from 2 to 26% calculated on a basis of the weight of the charging stock. It will be evident, therefore, that the yield of low boiling aromatics, which find extensive use in industry particularly as blending material for raising the antiknock value of the gasolines, may be increased to a point where such an operation is distinctly profitable by increasing the steam used.

The total products from the heating zone may be passed through a line 8 and a control valve 9 which may be used to vary the pressure desired and enter an enlarged chamber 10 in which the vaporous and nonvaporous reaction products are separated. This chamber may be provided with upper and lower removable manheads 11 and 12 respectively and a liquid draw line 13 containing control valve. 14. The reactions of decomposition are commonly of such a nature that considerable quantities of coke are produced, sometimes as high as from 180 to 190 lbs. per bbl. of charging stock, this varying againv with the conditions of operation and the amount of steam used. The process, therefore,will'be usually intermittent on account of the necessity for removal of coke accumulations although in some instances in which substantial percentages of neutral oils are present in the tar acids, a liquid residuum operation may be conducted in which case the liquid residuals may be continuously withdrawn through the line 13 containing control valve 14. The-vaporous products -from chamber 10 may pass through a line 15 containing control valve 16 and enter a primary fractionator 17 of a design and-capacity suitable for separating the entering vapors into overhead portions, adaptable to further processing by the second step of the process which will presently be described, and insufliciently converted intermediate refluxes which are returnedto the heating zone for further treatment. These latter fractions may be lwithdrawn from the bottom of fractionator 17 thi ough a line 20 containing control valve 21 and content of the entering vapors, the type of re-v ducing gas employed, etc. and may include any of the commoner metals or metal oxides employed in hydrocarbon conversion such as, for example, iron, nickel, cobalt, chromium, manganese, molybdenum, tungsten, tin, zinc, aluminum, etc. 'Ihe exact type of catalyst employed will be determined by the results desired but it may be pointed out that good results have been obtained with tinned iron.

Reducing gases' of varying types may be admitted to the vapor line prior to the treater through a line 26 containing a control valve 27. Such gases may be hydrogen, methane, natural gas, cracked gases, carbon monoxide, ue gas, etc., these gases serving to augment the reducing gas content of the vapors so that the succeeding hydrogenating or reducing reactions occurring in treater 25 may proceed to a greater extent.

The reactions occurring in sentially those of reduction of phenolic constituents to produce high yields of "low boiling aromatic hydrocarbons, the hydroxyl groups yielding water and the side chains such as methyl and ethyl groups yielding, in general, parafn hydrocarbons such as methane, ethane, etc. though some unsaturates may be produced such as ethylene. Treater 25 is provided with manheads ly be included Within the range of 650 to 850 F.

more or less and if desired or found advantageous the pressure may be stepped up by pumping means not shown so that considerably higher pressures are used than those obtaining in preceding portions of the equipment. Additional heat may be supplied at this -stage if necessary.

The mixture of vapors and gases from treater 25 may be conducted through a line 30 containing control valve 31 to a i'lnal fractionator 32 which is utilized to produce overhead fractions of desired boiling point range and further amounts of insufficiently converted reiluxes amendable to further heat treatment. i

The vapors of desired boiling point range may pass through a line 33 containing a control valve 34 andbe partially condensed by passage through a condenser 35, the cooled liquids and residual gases being conducted together through rundown line 36 and control valve 37 to receiver 38 in which liquids and gases are separated. The gases may be released at a regulated rate through a line 39 containing a control valve 40 and in some cases may be recycled for use in treater 25 though means for this recycling are not shown in the drawing. End point liquids may be withdrawn from the receiver through a line 41 containing control valve 42 and utilized in some cases ditreater 25 are esrectly as motor fuel after suitable treatment or in some cases treated with caustic soda to separate low boiling phenols which are then utilized in any manner to which they are suited.

The insufiiciently converted reiiuxes from final fractionator 32 may be withdrawn from the bottom thereof through a line 43 containing control valve 44 and leading to a pump 45, this pump discharging the fractions through a line 46 containing the control valve 47 to the inlet side of feed pump 3.

As an example of results obtainable by the operation of the present invention, a case may be cited involving the treatment of a. tar acid oil having the following characteristics:

Distinction analysis Percent dis- F.

tilled over This charging stock may be cracked in the primary unit at 175 lbs. pressure at a temperature of 885 F. at the exit of the heating element, an amount of water being added equal to 25% by weight of the charging stock.

The catalyst employed in the secondary treater may be tinned iron, the temperature employed therein 700 to 750 F. and the pressure substantially the same as that obtained in the primary cracking stage, allowing for differential drop due to uid friction.

By recycling `of intermediates both from the primary and the secondary fractionator, a yield of a. mixture of low boiling aromatic and phe invention and description of one of its operations will serve to accurately denne its scope and indicate to a large extent its value in the art to which it applies. However, since the process is applicable to the treatment of any mixture of phenolic compounds or mixtures of the same with hydrocarbons and since the apparatus used and the conditions of operation may be varied over a wide range, it is not intended that the foregoing descriptive matter and the example given are to be construed as limitations upon the broad scope of the invention. I claim as my invention: l. A process for converting tar acids into more valuable products which comprises heating the n tar acids in the presence of water or steam to between 850 F. and 900 F. under a pressure of from 50 to 250 pounds per square inch, thereby forming compounds boiling within the motor fuel range, and subjecting said compounds at from 650 F. to 850 F. to the combined action of a reducing agent and a reducing catalyst.

2. A process for converting tar acids into more valuable products which comprises heating the tar acids in the presence of water or steam to between 850 F. and 900 F. under a pressure of from 50 to 250 pounds per square inch, fractionating the vapors thus formed to condense fractions thereof boiling above the motor fuel range and returning resultant refiux condensate to the heating step, subjecting the fractionated vapors at between 650 F. and 850 F. to the combined action of a. reducing agent and a reducing catalyst, and condensing the thus treated vapors.

JACQUE C. MORRELL. 

